Cellulose derivative.



UNITED STATES PATENT EMIL KNOEVENAGEL, OF HEIDELBERG, AND HANS LEBACH, OF LUDWIGSHAFEN, GERMANY, ASSIGNORS TO THE FIRM OF KNOLL AND COMPANY, OF LUDWIGSHAFEN-ON-THE-RHIN E, GERMANY, A CORPORATION OF GERMANY.

' CELLULOSE DERIVATIVE.

Specification of Letters Patent.

Patentedfiune 16, 1908.

To all whom it may concern:

Be it known that we, EMIL KNOEVENAGEL, professor of chemistry, a subject of the German Emperor, residing at Heidelberg, in the Grand Duchy of Baden, Germany, and HANS LEBAOH, chemist, a subject of the German Emperor, residin at Ludwigshafen, in the Grand Duchy of Bavaria, Germany, have invented certain new and useful Improvements Relating to Cellulose Derivatives, of which the following is. a specification. I

It is well known that cellulose is capable of yielding acid derivatives, of which'in-particular the nitric acid and acetic acid derivatives have acquired technical importance. We have found, that derivatives of cellulose with organic acids may be formed, if cellulose or its closely allied conversion products, such as hydro-cellulose, oXy-cellulose, etc. be brought together and heated with the anhydrids of organic acids in the presence of volatile m0nobasic mineral acids By means of these volatile mono-basic acids. the formation of acidyl cellulose takes place, as it does by means of sulfuric acid in cases which have previously become known (see Franchimont, Ber. d. Deutsch. Chem. Ges. 14 page 1290 and Rec. Trev. Ohi'm. Pays. Bus. 18 page 472 Skraup, Ber. d. Deutsch Chem. Gas. 32 page 2413, Lederer, specifications'of German Patents 118538 and 120713, Farbenfabriken vorm. Bayer & (30., s )ecification of German Patent 153350) or y means of phenol-sulfonic acids (French Patent specification 324862). In comparison with these acidylizing agents the agents employed by us in the preparation of acid derivatives of cellulose in the manner hereinafter described offer important advantages, which consist in the fact, that the solutions prepared by their aid may be kept for months without suffering any loss of viscosity and can be also solidified by evaporation of the solvent at not too high a temperature Without decomposition. Solutions prepared by means of these vsubstances are therefore adapted to be spun into artificial silk, either directly in the air or in suitable precipitating agents, and may be employed directly for the preparation of lilms and celluloid compositions, whereas in the known process the acid esters of cellulose had to be first precipitated and freed by washing from the adhering acids, before solutions which could be spun, films or celluloid compositions could be prepared from them.

With the use of volatile mono-basic acids, such for example, as hydrochloric acid, nitric acid or mixtures thereof, this advantage is to be ascribed to the volatility of the acid employed, which does not enter into chemical combination in the acidylizing process, and also to their mono-basicity, which causes any quantities of the acids which may combine with the cellulose to completely lose their acid properties at the same time, which is not the case with polybasic acids.

When volatile mono-basic acids are employed for the preparation of viscous soluble acidyl-cellulose according to the resent invention these acids are employe in quantities which in general corres 0nd to 0.1 to 0.3 parts by weight of the cellu ose employed, and the acidylation is carried out at temperatures between 40 and 80 C. If attem ts be, made to acidylize with substantia y smaller quantities than 0.1 partsof the acid to 1 art of cellulose (similar to the examples in t 1e specification of French Patent 0. 319648, e. g. with hydrochloric acid in place of sulfuric acid) no acidylization at all takes place at ordinary temperatures, even after a comparatively long time. If, under otherwise equal conditions, viz: wh1le using less than 0.1 part of the acid to 1 part of cellulose, the reaction temperature be raised to 70 C. for example, only incomplete acidylation takes place, even after a somewhat protracted period of time. The use of hydrochloric acid in acetylizationhas also become known in another form by a research of Zd. H. Skrau and his collaborators (Wiener M onptshe te Ohe'mie XXVI 1905. 1450).. I

Whereas, however, the above investigators obtained at ordinary temperature by the action of acetic anhydrid saturated with hydrochloric acid gas, chloracetyl derivatives of cellulose and on prolongated action even secondary products thereof,'we on the contrary, obtain pure acidyl derivatives, owing to the use of substantially smaller quantities of acid.

The following examples may serve to explain the rocess:

Examp e I: Into a mixture of 5 parts of acetic anhydrid and 4 parts of lacial acetic acid are led 0.1 to 0.2 parts of l acid gas, and after this 1 part of cellulose,

iydrochloric -drid an being cooled) are added from 0.1 to 0.2 parts e. wadding, is added. Solution asacetylce lulose takes place at about 70 0. within 30 to 40 hours.

Example 11: To 5 parts of propionic anhydrid and 4 to 5 parts of glacial acetic acid is added as much concentrated aqueous hydrochloric acid, as corresponds to 0.1 parts of hydro en chlorid. After the addition of 1 art feellulose, solution as propionyl-celluose takes place at about 70 C. in 12 to 24 hours.

Examdple III: To 5 parts of acetic anhy- 4. to 5 parts of acetic acid (while of an approximately 65 per cent. nitric acid and 1 part of cellulose, and the whole brought into a bath of about 70 C. After 1 to 3 days about 0.1 arts of the same acid are again added. T e formation of a com letely colorless very viscous solution as acety cellulose takes place in 4 to 6 days.

Example IV: To a cold mixture of 5 parts of acetic anhydrid and 4 to 5 parts of acetic acid are added 0.1 to 0.2 parts of a cold mixture of say 3 partsof concentrated hydrochloric and 1 )art of concentrated nitric acid, and 1 art 0 cellulose. At about 70 C. a clear viscous solution is obtained in 5 to 15 hours.

- The chemical reactions taking place in Examples 1, III and IV may be represented by the following equation:

( 310 3X(o.11 co ,o '4- The effect of the volatile mono-basic mineral acids at a high temperature cannot well be illustrated by chemical equation. The

chemical reaction, as far as it is capable-of illustration by chemical equation, is wellknown, but under the influence of monobasic mineral acids and heat the acid derivatives of cellulose resulting from our process acquire valuable properties, which they do not possess under the conditions hitherto known.

What we claim'isz- 1. Theprocess for the manufacture of cellulose'este'r solutions from cellulose by the action of or anic acid anhydrids in the presence of V0 atile mono-basic mineral acids, which consists in adding to an organic acid anhydrid in solution a volatile mono-basic mineral acid corresponding in weight to from 0.1 to 0.3 ployed, and causingzthe resulting acid mixture to act on the cellulose at a temperature ranging between 40 C. to 80 0., substantial y as described. I

2. The process for the manufacture of acetyl-cellulose solutions from cellulose by the action of acetic anhydrid in the presence of hydrochloric acid, which consists in adding to the acetic anhydrid in solution hydrochloric acid corresponding in weight to from 0.1 to 0.3 arts of the cellulose employed, and causing the resulting acid mixture to act on the cellulose ata temperature ran ing between 40 C. and 70 0., substantially as described.

In testimony whereof we have hereunto set our hands in the presence of two subscribing witnesses.

EMIL KNOEVENAGEL.

HANS LEBAOH. Witnesses:

H. W. HARRIS, Jos. H. LEUTE. 

